全文获取类型
收费全文 | 4262篇 |
免费 | 170篇 |
国内免费 | 23篇 |
专业分类
化学 | 3084篇 |
晶体学 | 35篇 |
力学 | 113篇 |
综合类 | 1篇 |
数学 | 638篇 |
物理学 | 584篇 |
出版年
2023年 | 42篇 |
2022年 | 41篇 |
2021年 | 58篇 |
2020年 | 91篇 |
2019年 | 83篇 |
2018年 | 51篇 |
2017年 | 47篇 |
2016年 | 144篇 |
2015年 | 132篇 |
2014年 | 151篇 |
2013年 | 221篇 |
2012年 | 267篇 |
2011年 | 306篇 |
2010年 | 175篇 |
2009年 | 154篇 |
2008年 | 239篇 |
2007年 | 253篇 |
2006年 | 237篇 |
2005年 | 195篇 |
2004年 | 181篇 |
2003年 | 143篇 |
2002年 | 153篇 |
2001年 | 97篇 |
2000年 | 94篇 |
1999年 | 78篇 |
1998年 | 56篇 |
1997年 | 41篇 |
1996年 | 35篇 |
1995年 | 51篇 |
1994年 | 48篇 |
1993年 | 37篇 |
1992年 | 33篇 |
1991年 | 43篇 |
1990年 | 41篇 |
1989年 | 33篇 |
1988年 | 14篇 |
1987年 | 21篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 27篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 26篇 |
1979年 | 21篇 |
1978年 | 22篇 |
1977年 | 36篇 |
1975年 | 18篇 |
1974年 | 14篇 |
1973年 | 14篇 |
1972年 | 13篇 |
排序方式: 共有4455条查询结果,搜索用时 15 毫秒
1.
2.
Marcel Oliver 《Theoretical and Computational Fluid Dynamics》1997,9(3-4):311-324
The so-called lake equations arise as the shallow-water limit of the rigid-lid equations—three-dimensional Euler equations
with a rigid-lid upper boundary condition—in a horizontally periodic basin with bottom topography. We prove an a priori estimate in the Sobolev space H
m
for m≥ 3 which shows that a solution to the rigid-lid equations can be approximated by a solution of the lake equations for an
interval of time which can be estimated in terms of the initial deviation from a columnar configuration and the magnitude
of the initial data in H
m
, the gradient of the bottom topography in H
m+1
, and the aspect ratio of the basin. In particular, any solution to the lake equations remains close to some solution of the
rigid-lid equations for an interval of time that can be made arbitrarily large by choosing the aspect ratio of the basin small.
Received 10 October 1996 and accepted 15 May 1997 相似文献
3.
The consecutive reactions of (CH3)2Si(OC2H5)2 and CH3Si(OC2H5)3 with methoxide ions were investigated in methanol solutions. The reverse transesterification reactions with ethoxide ions could be neglected in both cases since the concentration of ethoxide in methanol solution was assumed to be low due to the fast equilibrium reaction C2H5O? + CH3OH ? C2H5OH + CH3O?. The progress of the reactions was followed by monitoring the formation of ethanol with a Fourier-transform infrared spectrometer. All rate constants were determined at 295 K. The reactions between the dialkoxydimethylsilanes and methoxide ions were assumed to consist of two consecutive steps that can be represented by the net reaction; (CH3)2Si(OC2H5)2 + 2CH3O? → (CH3)2Si(OCH3)2 + 2C2H5O?. The two consecutive rate constants were established as 1.93 ± 0.12M?1s?1 and 1.00 ± 0.12M?1s?1, respectively. The consecutive rate constants for the reactions between the trialkoxymethylsilanes and methoxide ions can be written according to the total reaction; CH3Si(OC2H5)3 + 3CH3O? → CH3Si(OCH3)3 + 3C2H5O?. The three rate constants corresponding to each consecutive step were established as 1.12 ± 0.09 M?1s?1, 0.82 ± 0.10 M?1s?1, and 0.51 ± 0.06 M?1s?1, respectively. © 1995 John Wiley & Sons, Inc. 相似文献
4.
Fixed-frequency and threshold photoelectron spectra have been recorded for ionization from the S ls shells in SF6, CS2 and COS, the Si 1s shells in SiH4 and SiCl4 and the Cl 1s shell in SiCl4 using synchrotron radiation. Fixed-frequency spectra generally showed a single strong ionization feature with associated weak satellite structure due to excited ionized states. Threshold spectra closely resembled X-ray absorption spectra but with an additional feature due to direct ionization. In cases where resonant process enhanced the NEXAFS spectrum direct ionization was not observed. 相似文献
5.
6.
7.
8.
9.
Julie Clutterbuck Oliver C. Schnürer Felix Schulze 《Calculus of Variations and Partial Differential Equations》2007,29(3):281-293
We prove stability of rotationally symmetric translating solutions to mean curvature flow. For initial data that converge
spatially at infinity to such a soliton, we obtain convergence for large times to that soliton without imposing any decay
rates.
The authors are members of SFB 647/B3 “Raum – Zeit – Materie: Singularity Structure, Long-time Behaviour and Dynamics of Solutions
of Non-linear Evolution Equations”. 相似文献
10.
Ohne Zusammenfassung 相似文献